Aerial supporting structure for line construction and maintenance workers



Get. 24, 1961 R. R. VOGAN 3,005,512

AERIAL SUPPORTING STRUCTURE FOR LINE CONSTRUCTION AND MAINTENANCE WORKERS Filed May 31, 1960 2 Sheets-Sheet 1 INVENTOR 3? BY 7L 5 ATTORNEYS 00L 1951 R. R. VOGAN 3,005,512

AERIAL SUPPORTING STRUCTURE FOR LINE CONSTRUCTION AND MAINTENANCE WORKERS Filed ivlay 31, 1960 2 Sheets-Sheet 2 W I illillilili 074 INVENTOR I p 4% 7 ATTORNEYS United States Patent 3,005,512 AERIAL SUPPORTING STRUCTURE FOR LINE CONSTRUCTION AND MAlNTE- NANCE WORKERS Rex R. Vogan, Abington, Pa, assignor, by mesne assignments, to Asplundh Tree Expert (30., Jenkintown, Pa., a corporation of Pennsylvania Filed May 31, 1960, Ser. No. 32,751 7 Claims. (Cl. 182-2) The present invention relates to equipment for elevating a man and supporting him from a position on the ground in an elevated location for work on or around electrically charged overhead wires.

In equipment of the type referred to it is common practice to provide a pair of elongated boom-like members which are pivoted or articulated together at one end. At the opposite end one of the members is pivotally mounted upon a mobile platform or base while the other member pivotally carries at its outer end a suitable supporting structure or basket in which the Workman rides. The member which is pivoted on the mobile base will be referred to hereinafter as the lower member while the other member which is articulated thereto Will be referred to as the upper member. All of the pivots are horizontally disposed so that the lower member can swing upwardly and downwardly in a vertical plane on the mobile platform, the upper member can swing upwardly and downwardly in a vertical plane on the outer end of the lower member and the basket structure can swing in a vertical plane on the outer end of the upper member so as to main- ,tain a level position at all times regardless of the position to which it is carried by the booms.

The booms are raised and lowered by suitable motor means and they can be swung down to a position where both members are substantially horizontal, and each boom member may swing on its pivot throughout a substantial arc in order to provide for the largest possible combination of movements and thereby enable the workman to be readily located in the most advantageous position relative to the Work to be performed. This can be provided for in various Ways by those skilled inthe art of mechanics and typical equipment for the purpose is illustrated in the copending application of Lester Asplundh Serial No. 833,347 as well as in US. patents to Miller No. 2,450,152, to Stemm No. 2,616,768, to Troche No. 2,881,- 030 and to Troche No. 2,915,137.

The present invention is particularly useful in connection with equipment of the character above described, but before reciting the principal objects of the invention attention is called to the following problems which must be met. The workmans supporting structure must be strong enough to support not only the weight of the man but also whatever equipment he may be using. At the same time, the structure should be relatively light in weight so that the machine as a whole need not be made of excessively heavy units. This is of particular importance when it is realized that the basket containing the workman and his tools may be suspended in a position where the leverage eXerted is extremely high. Beyond the foregoing, the basket must be of very high dielectric strength in order to protect a man from danger in case he should come in contact with a high tension wire. Still further, the equipment must be capable of use in all kinds of weather with-.

out in anyway havin either its structural strength or its dielectric strength impaired, the latter particularly being liable to impairment in case of rain or other weather conditions which introduce moisture into the basket or its supporting structure. In connection with the matter of rain or moisture, it is also important to provide means for disposing of the water without providing drainage Patented Oct. 24, 1961 apertures in the basket structure for the reason that the presence of an aperture may often be a danger in that a heavily charged tree branch or a loose wire may project through such an aperture and endanger the life of the workman.

With all of the foregoing in mind the objects of the invention can be better understood and more fully appreciated. These objects include the provision of equipment for aerial supporting structure of the character described in which the workmans platform or supporting basket can be structurally strong yet light and readily maneuverable, of high dielectric strength, absolutely water-impervious, without apertures or openings through which wires or branches may enter the basket and easily. emptied of any water which may accumulate in the basket during inclement weather.

Another important object is to provide equipment of this type where the part upon which the Workman stands may be easily removed for the purpose of test or replacement as well as for emptying out any water which may have collected therein.

Still another object is to provide what might be termed dual construction in a basket of this kind, i.e. a construction in which the physical strength required is imparted by an outer or frame member andthe dielectric strength by an inner or liner member. This makes it possible to form the outer or frame member of material best suited for this purpose but without making it unusually heavy or thick in an effort to add the required dielectric strength. For instance, it has been the practice to make these baskets of suitable plastic material reinforced with glass fibers on the theory that both physical strength and dielectric strength can be so imparted to the structure. Furthermore, the practice has been to make such baskets by what is called a hand-laid-up process and obviously the materials employed are not homogeneous. In addition, the quality of the results secured by this hand method depends entirely too much upon the individual who is doing the work. For example, if any air bubbles or voids are introduced in the laying-up process they will introduce weaknesses especially from a dielectric standpoint. Beyond this, such built up units as presently manufactured tend to a certain porosity and will ofen pick up moisture over a period of time which, of course, impairs their dielectric efliciency. Still further, such a unit, if struck by a heavy object, may develop small cracks which, even when not visible to the eye, will introduce dangerous dielectric weakness. To overcome these diificulties present methods of manufacturing baskets for this purpose have involved making them considerably heavier than necessary, but even with this heavier structure success has not always been attained.

In contradistinction to the foregoing practice, my dual construction involves the provision of the outer member already referred to and also an inner liner or insert formed of some suitable and completely homogeneous dielectric material which is inherently strong and absolutely waterimpervious, such for example as polyethylene, glass or hard rubber. In this way the insert also may be made of less weight because it does not have to provide the complete structural strength required while still providing the needed high dielectrical'ly constant value so that both the frame and the insert need be characterized by having only the strength which each requires for the job it has to perform and this without the necessity of making either unduly heavy in nature. Furthermore, by adopting such dual construction the insert can be readily removed and replaced or removed for the purpose of testing its dielectric efliciency or for emptying from it any water which may have accumulated during service without resorting to the tedious and inefiicient bailing and swabbing procedure heretofore in use where the basket has no drainage openings.

How the foregoing objects together with such other objects as may appear hereinafter or are incident to my invention are attained will now be described in connection with the accompanying drawings, wherein:

FIGURE 1 is a somewhat diagrammatic side elevation of aerial supporting structure of the kind to which my invention relates showing a workman in elevated location near overhead wires in the full line position and in dot and dash lines in a position where the basket insert can be readily removed;

FIGURE 2 is a vertical section through the basket structure per se showing the outer framework and the inner removable insert or liner, the section being taken on the line 2-2 of FIGURE 3;

FIGURE. 3 is a side elevation of the basket structure illustrated in FIGURE 2;

FIGURE 4 is a bottom view of the basket structure illustrated in FIGURES 2 and 3; 7

FIGURE 5 is a perspective view of the basket insert; and

FIGURE 6 is a section on the line 6-6 of FIGURE 3.

In FIGURE 1 of the drawings I have illustrated a truck T upon which the lifting mechanism has been mounted. The truck carries an upright mast or pylon 7L This pylon may be rotated in any preferred manner familiar to those skilled in the art.

At the top of the pylon I mount a lower boom member 8 upon a horizontal pivot axis 9. The boom member 8 can be raised or lowered in a vertical plane around the axis 9 by means of a motor mechanism which includes a cylinder 10 and a cooperating piston 11 the former of which is pivoted to the pylon at the point 12' and the latter to the boom 8 by means of a suitable bracket and pivot connection indicated at 13.

At the upper end of the lower member S'I pivot the upper member 14 upon a horizontal axis 15 so that the upper member also can be swung upwardly and downwardly in a vertical plane. The axis passes through the adjacent ends of the twomembers 8 and 14 and thereby articulates them together, the arrangement being such as to bring the two members into side by side relationship when the device is in neutral or lowered position indicated by the dot and dash lines at 16.

The upper member 14 can be swung on its axis 15 by means of a motor device which includes a cylinder 17 and a piston 18 which are carried onthe side of the lower member 8 and interconnected with the member 14 through the medium of a cable 19 and a sheave 20.

At the outer end of the upper boom 14 is pivoted the workmans basket indicated as a whole by the character B. A workman is shown in the basket in position near the overhead wires 21 at the top of a pole 22.

i The details of the basket are shown in FIGURES 2 to 6, inclusive, from examination of which it will be seen that I have. formed it of two major parts, namely, an outer framework 23 and an inner liner or insert 24. The outer frame is preferably built up out of a suitable dielectric plastic material reinforced with glass fibers and should be constructed so as to provide the structural strength which may be necessary to support the weight of the man in eluding whatever equipment and tools he may require for the job in hand. However, with my invention, it need not be of sufiicient mass or weight to provide the complete dielectric quality which is required in equipment of this kind. This is hard to secure in a glass fiber reinforced plastic article because of the lack of homogeneity and the fact that the manufacturing technique involves a hand-laid-up process such as is presently employed by those skilled in this art. Match-molding of a basket from glass fiber, suitable resin and/or cloth might be feasible but such match-molding requires a tremendous investment in molds and presses which would be excessive in cost in order to mold a unit of the size of the basket required.

Near its top the frame 23 may be provided with thickened reinforcing ribs 25 and at the top it may have a thickened portion 26 and at the bottom another thickened portion 27. To the portions 25 is secured the shaft 28 by means of which the basket is pivoted at the outer end of the upper boom, the arrangement being such as to make this pivot a horizontal axis which parallels the axes 9 and 15 of the boom structure. The shaft 28 is trunnioned in any suitable manner in the upper end of the outer boom and a pulley or sheave 29 (see FIGURE 1) is keyed or otherwise secured to the shaft at the point indicated as a keyway 39 in FIGURE 2. At its inner end the shaft has a flange 2841 by means of which it can be bolted to the thickened portions 25 of the frame 23 as most clearly shown in the enlarged view of FIGURE 6. The heads of the bolts are buried in the thickened portions 25 and should be sealed in place with fiberglass reinforced resin plugs 35 as shown to best advantage in FIGURE 6.

The insert or liner 24 is formed of any suitable completely homogeneous and waterdmpervious material of high dielectric strength such as polyethylene, glass or hard rubber and, as clearly shown in the drawings, this insert is formed without aperture of any kind even in the bottom wall 24a thereof. Furthermore, the bottom is provided with exterior reinforcing ribs 31 which extend radially outwardly from a circular hub 32 to the perimeter of the insert. This construction provides the strength required for supporting the man together with his equipment and tools in which connection it should be noted that the frame 23 is preferably formed without a bottom as shown in FEGURE 2. At its top the insert has an annular laterally extending flange 33 which is adapted to rest upon the thickened portion 26 of the framework as shown in FIGURES 2 and 3. This flange must be of suflicient dimension and strength to carry the weight of the insert itself as well as the weight which may be placed therein, including the weight of the Workman.

The frame and the insert are of substantially the same shape md it will be noted that they taper slightly from the bottom to the top so that they may be described as upwardly flaring. It should also be noted that the insert while it fits the frame with reasonable snugness is so formed as to leave a space between the inner wall of the frame and the outer wall of the insert indicated by the reference character 34 in FIGURES 2 and 6. This space is important but it need not be of very great dimension. In fact, when the insert is centered in the frame 23 the width of the space 34 may be approximately The structure is such as to render the insert readily removable and replaceable and its weight is such that this can be done by the workman merely by placing his fingers under the flange 33 and lifting the insert out of the frame. This operation is roughly indicated in dotted lines in FIGURE 1. The insert when so removed can be emptied of any water that may have accumulated therein merely by pouring it out after which the insert may be returned to its position in the frame 23.

By virtue of the ready removability of the insert it is also possible to make periodic checks of its dielectric quality and this without taking the truck and the entire equipment out of service as is now necessary when checking the condition of the baskets at present in use which are formed of one piece. With my improved construction the testing can be accomplished by taking the insert to a specially prepared testing center or laboratory and during the testing procedure a replacement insert may be substituted for the one removed, so that the equipment as a whole is not laid up during the testing period. This is a very important feature of my invention because the equipment as a whole is relatively expensive and must be kept in operation as continuously as possible in order to justify its cost.

Incidentally, the testing of the inserts is preferably done by what is known as the immersion method where a steel tank of sufficient size is filled with water and the insert lowered into the water and itself filled with water.

A lead from a transformer used in the testing procedure is attached to the tank and another lead is attached to the inside of the liner after which a high potential is applied to the circuit which should be sufficient to immediately disclose the minutest flaw if any exists. Such a test, of course, is quite impossible with baskets made of one piece as heretofore customary in the art because it is a major operation to remove a basket of this kind from the boom to which it is attached and beyond this such removal would tie up the entire equipment while the test is in progress.

I should also explain that homogeneous, water-impervious basket inserts such as I have developed do not tend to absorb moisture which absorption of moisture has been a problem with the old style single unit baskets because such single unit baskets, by virtue of the very man ner of their fabrication, cannot be made completely water-impervious.

The importance of my removable insert construction is further emphasized by the fact that leveling cables 36 and 37 are reeved between the several axes 9, 15 and 29 in a manner familiar in this art so that the basket B will always be maintained in a level position regardless of the location to which it is raised or lowered by movement of the boom construction. It is this necessity for positively maintaining the basket steady and in level position which gives rise to the difliculty of emptying any water which may accumulate in the basket. Because of the leveling mechanism the basket cannot be turned over or tipped sufiiciently to pour out the Water so long as it is mounted on the end of the upper boom. With my invention, however, this difficulty is overcome because the basket is of duplex construction which makes it possible to remove the insert and empty out the water without the necessity of removing the entire basket from the boom.

I claim:

1. In a device for elevating a man and supporting him from a position on the ground in an elevated location for work around electrically charged overhead wires, the combination of a truck, a boom pivoted on the truck, a workmans basket pivoted on the outer end of the boom, means for raising and lowering the boom, means for maintaining the basket in level position as the boom is raised and lowered, and a readily removable and replaceable, imperforate, dielectric liner constructed of water-impervious material fitting the interior of the basket.

2. A basket for supporting a workman on the outer end of a pivoted boom in position for work on or around electrically charged overhead wires, said basket comprising an open-topped, outer, structurally strong, loadcarrying framework having a laterally extending arm by means of which the basket is swingably hung on the outer end of the boom, and a readily removable and replaceable open-topped, imperforate and water-impervious liner fitting the interior of the load-carrying framework and having a dielectric strength suflicient to prevent short circuiting from the wires to the framework through the body of the workman even in the presence of water.

3. A basket according to claim 2 wherein the framework and the liner are constructed with upwardly flaring Walls.

4. A basket according to claim 3 wherein the liner is provided at its top with an outwardly extending flange adapted to rest upon the upper edge of the framework.

5. For a line-construction or maintenance workers boom-supported basket; a readily removable and replaceable open-topped, imperforate, water-impervious basket liner constructed of material having a dielectric strength sufiicient to prevent short circuiting from the line to the basket through the body of the workman even in the presence of water.

6. A basket liner according to claim 5 having an outwardly extending supporting flange at the top.

7. A basket liner according to claim 5 having an outwardly extending supporting flange at the top and reinforcing ribs on the bottom.

References Cited in the file of this patent UNITED STATES PATENTS 853,173 Jacobi May 7, 1907 2,940,539 Richey June 14, 1960 2,946,474 Knapp July 26, 1960 

